substructure
[noun]
Synonyms: base, basis, bottom, foundation, groundwork, infrastructure, seat, substratum, substruction, understructure

---

Antonyms: superstructure

[TahlilGaran] English Synonym Dictionary ▲

sub‧struc‧ture /ˈsʌbˌstrʌktʃə $ -ər/ noun [countable]

1. one of the structures (structure¹(3)) within a society or organization that combines with others to form a whole

2. a solid base under the ground, that supports a building above the ground ⇒ superstructure

[TahlilGaran] Dictionary of Contemporary English ▲